Track type tractors are one type of machine that utilize an idler recoil system in order to better allow the tracks of the machine to interact with variable loads encountered when the machine is being maneuvered over the ground. A typical track system may include a forward idler that is supported by a track roller frame assembly about which the track is mounted. The idler may typically be connected to a yoke that may slide fore and aft within the track roller frame assembly in order to react to various loads that are transmitted from the track to the idler. The yoke in turn acts upon a spring that is compressed when the idler and yoke are pushed into the track roller frame assembly. The spring then pushes back on the yoke and idler to recoil both toward their undisturbed operating configuration.
In the past, recoil springs were usually made up of heavy mechanical springs. More recently, such as shown in co-owned U.S. Pat. No. 7,252,349, gas springs have been gaining wider acceptance and usage. Gas springs have the advantage over conventional mechanical springs in that their pre-load can be adjusted by adding or removing gas, such as nitrogen, to and from the gas spring. The '349 patent is also of interest for teaching the inclusion of a track tensioning feature located between the yoke and the gas spring of the recoil system. In particular, a grease volume may be filled with a selected volume of grease to adjust the effective distance between the gas spring and the yoke, thereby adjusting a forward position of the idler, and consequently the tension in the track that is mounted about the track roller frame assembly.
Although a variety of track roller frame assemblies and their associated recoil systems have performed well over many years, there remains room for improvement, particularly in the areas of assembly, packaging and servicing. For instance, the '349 patent teaches a recoil and adjustment system for a track type tractor in which the various components of the recoil system are individually attached within the track roller frame housing. This construction can make assembly more cumbersome and give rise to possible misalignment compensation strategies associated with a line of force from the idler, through the yoke, through the tensioning adjustment system and finally to the recoil gas spring.
Co-owned U.S. Patent Application Publication 2009/0200862 shows another incremental improvement in that the idler recoil and track adjustment device is a separate unit that is preassembled and installed into a track roller frame as an assembled unit at the time of manufacture of the track type machine. In this design, the remote end of the unit is supported in a socket defined by an internal surface of the track roller frame, while the yoke end is supported by, and attached to, a bulkhead of the track roller frame by an array of fasteners that surround the recoil shaft. While this design has shown considerable promise, there remains room for improvement, especially with regard to packaging, servicing, installation, cost and performance.
The present disclosure is directed toward one or more of the problems associated with recoil systems for the machines including but not limited to assembly, packaging and servicing.